1. Field of the Invention
The present invention relates to a continuously variable transmission equipped with a forward-speed/reverse-speed changeover mechanism.
2. Description of the Related Art
As a technique associated with this type of continuously variable transmission, a belt-type continuously variable transmission disclosed in JP-A-10-274319 can be given as an example. The transmission mechanism of this continuously variable transmission is constructed in such a way that a primary shaft and a secondary shaft are disposed in parallel with each other within a casing, and an endless belt is suspended between a primary pulley provided on the primary shaft and a secondary pulley provided on the secondary shaft. The primary pulley and the secondary pulley are each constructed of a fixed sheave and a movable sheave. The movable sheave is made movable by an actuator in the axial direction. By the oil-pressure, etc. supplied to the actuator, the spacing between corresponding ones of the sheaves is adjusted such that the speed-change ratio can be varied continuously.
The drive force of an engine is transmitted to a drive-wheel side sequentially through a torque converter, an input shaft that is a rotating shaft, a forward-speed/reverse-speed changeover mechanism comprised of a planetary-gear mechanism, connected to an output side of the input shaft, the above-described speed-change mechanism, differential gears, etc.
The rotation of a turbine runner, output from the torque converter, is output to the primary shaft by being selectively changed over, through the forward-speed/reverse-speed changeover mechanism, to either one of a normal rotating direction (the forward direction of the vehicle) or a reverse rotating direction (the reverse direction of the vehicle).
Incidentally, the concrete construction is as follows. First, the input shaft is connected to the turbine runner, and the input shaft has a sun gear on the outer-periphery of its output side. Also, the planetary-gear mechanism includes pinion gears, a carrier, and a ring gear. The pinion gears mesh with the sun gear and the carrier is connected to an input side of the primary shaft. Among these members, the carrier and the input shaft are mutually connectable or disconnectable by a clutch. Also, the rotation of the ring gear can be regulated by a brake. By controlling operations of the clutch and brake independently, it is possible to change the rotating direction of the carrier, i.e. the rotating direction of the primary shaft to the normal or reverse rotating direction with respect to the input shaft.
As illustrated in FIG. 5, the continuously variable transmission disclosed in the Japanese Patent Publication is constructed in such a form wherein a casing 101 is formed by connecting a main casing 101a and a sub-casing 101b. The above-described forward-speed/reverse-speed changeover mechanism 102 is incorporated into a brake support 104 shaped like a cup flared from and about the primary shaft 103. The brake support 104 is disposed within the main casing 101a in a state of being supported by the sub-casing 101b by means of bolts 105. An input end of the primary shaft 103 is connected to the carrier of the forward-speed/reverse-speed changeover mechanism 102. Also, the input end of the primary shaft 103 is rotatably supported by the brake support 104 through a bearing 106.
In the belt-type continuously variable transmission, a strong clamping force is imparted to the pulley for the purpose of preventing the slip of the belt. For this reason, the tension of the belt is necessarily increased with the result that a force causing the primary shaft and the secondary shaft to move toward each other acts upon these shafts. As a result, a high magnitude of load acts upon the bearings as well that support the primary and secondary shafts.
On the other hand, as apparent from the figure (FIG. 5), the bearing 106 for supporting one end (the rightward end in the figure) of the primary shaft 103 is supported, as if it were a cantilever, by the sub-casing 101b through the brake support 104. However, there was the problem that, due to the above-described tension of the belt, the brake support 104 was flexed and resultantly the bearing 106 shifted out of its regular position. As a result of this, the belt became mis-aligned and partial (uneven) contacts thereof occurred, with the result that the cone surface of the belt or pulley (the surface or surfaces over which the belt makes its contact with the pulley) became deteriorated in a short period of time.
Also, this belt-type continuously variable transmission has a structure that two members share the function of the input shaft. The detailed construction is as follows. First, as illustrated in FIG. 5, a reaction shaft support 101c, connected to the sub-casing 101b, is extended to the not-illustrated torque converter side (the rightward side in the figure) along an outer surface of the input shaft 107, and supports a stator of the torque converter. Further, one end (the rightward end in the figure) of the input shaft 107 is supported by the sub-casing 101b via the reaction shaft support 101c and a not-illustrated bearing provided between the reaction shaft support 101c and the input shaft 107. Also, the other end (the leftward end in the figure) of the input shaft 107 is supported by the brake support 104 via the bearing 106, the primary shaft 103, and the bearing 27 provided between the primary shaft 103 and the input shaft 107.
Here, the reaction shaft support 101c and the brake support 104 are positioned with respect to the sub-casing 101b. However, each of the bearing for supporting the one end (the rightward end in the figure) of the input shaft 107, the bearing 106 for supporting the one end (the rightward end in the figure) of the primary shaft 103, and the bearing 27 provided between the primary shaft 103 and the input shaft 107 contains the part-precision error and assembling error within a prescribed permissible range. For this reason, the center axes of these bearings are not in coincidence with one another, with the result that there was the problem of the input shaft 107 becoming deteriorated in terms of the centering precision. It is to be noted that it is difficult, with an ordinary attaching operation, to cause the center axes of these bearings to coincide with one another with high precision. So, there was conventionally a certain limit to enhance the centering precision of the input shaft 107.
An object of the present invention is to provide a continuously variable transmission that can maintain the bearing members of the primary and secondary shafts at their regular positions despite the tension or tensile force of the belt, and maintains the belt alignment as it is being apt, thereby enhancing the durability, especially a bearing structure of the belt-type continuously variable transmission.
Another object of the present invention is to provide a continuously variable transmission that can obtain the centering precision of each rotating shaft at very high accuracy.
To attain the above object, according to the first aspect of the present invention, there is provided a continuously variable transmission including, within a casing, a continuously variable transmission mechanism that includes a primary pulley provided on a primary shaft, a secondary pulley provided on a secondary shaft, and a belt suspended between both pulleys and enabling the transmission of a motive force between the pulleys, and that, by changing-the groove width of one of the primary pulley and secondary pulley relative to the groove width of the other, enables continuous adjustment of the speed-change ratio, and a motive-force connection/disconnection mechanism that, by being connected to either one of the primary shaft and the secondary shaft, enables connection/disconnection between an input side element for the motive force and an output side element for the motive force, the continuously variable transmission comprising, a housing member fixed within the casing and that accommodates therein the motive-force connection/disconnection mechanism and rotatably supports, via a bearing member, the one of the primary shaft and the secondary shaft that has been connected to the motive-force connection/disconnection mechanism, and a load-receiving element that is provided on an imaginary line that perpendicularly intersects the one of the primary shaft and the secondary shaft and passing through the bearing member or a vicinity thereof and, between the housing member and the casing member, and receives a force acting upon the housing member toward the side of the other of the primary shaft and the secondary shaft.
The tension of the belt of the continuously variable transmission acts upon the primary shaft and the secondary shaft. Therefore, a force that acts toward the other-shaft side from the one shaft thereof via the bearing member also acts upon the housing member for supporting one of those shafts. Accordingly, this housing member is required to have a rigidity high enough to hold the bearing member at its regular position against the tension of the belt. That force which acts upon the housing member is directly received by the load-receiving element that is provided on the imaginary line that perpendicularly intersects the one of the primary shaft and the secondary shaft and passes through the bearing member or a vicinity thereof, between the housing member and the casing member. As a result of this, the housing member is prevented from being flexed and resultantly it becomes possible to hold the bearing member at its regular position.
Also, according to the second aspect of the invention, there is provided a continuously variable transmission wherein the load-receiving element is formed at least at a position opposing the side of said other of the primary shaft and the secondary shaft.
Accordingly, in the case where the motive-force connection/disconnection mechanism is connected to the primary shaft, the force acting toward the secondary shaft side works upon the housing member for supporting the primary shaft via the bearing member. However, because the load-receiving element is formed at least at the position opposing the secondary shaft side, the force acting upon the housing member toward the secondary shaft side is reliably received by the load-receiving element. Resultantly, the bearing member can be held at its regular position. On the other hand, in the case where the motive-force connection/disconnection mechanism is connected to the secondary shaft, because the load-receiving element is formed at least at the position opposing the primary shaft side, the force acting upon the housing member toward the primary shaft side is similarly received by the load-receiving element. Resultantly, the bearing member can be held at its regular position.
Also, according to the third aspect of the invention, there is provided a continuously variable transmission wherein the load-receiving element is constructed of an inner-peripheral portion of the casing and an outer-peripheral portion of the housing member that engages the inner-peripheral portion of the casing.
Accordingly, it is possible to construct the load-receiving element simply without using any other parts therefor.
Also, according to the fourth aspect of the invention, there is provided a continuously variable transmission including a rotating shaft that rotates upon receipt of a driving force from a driving source, a rotation changeover mechanism that has a gear mechanism connected to the rotating shaft and that enables changing of the rotating direction of an output shaft via this gear mechanism, and a speed-change mechanism that transmits the driving force from the driving source to the output shaft by continuously changing the rotation speed thereof, the continuously variable transmission comprising a support member that rotatably supports a one-end side of the rotating shaft, a case member that accommodates, therein, the rotation changeover mechanism and that rotatably supports an other-end side of the rotating shaft, and a fixing element provided between the support member and the case member and attaching the support member to the case member as well as positioning the support member with respect to the case member.
Accordingly, the support member is directly positioned with respect to the case member. Therefore, as the support member is attached, the centers of the bearings can be made to coincide with one another through the intermediary of those two members with high precision. The centering precision of the rotating shaft is thereby greatly enhanced. Also, as a result of this, it is possible to lessen the intermeshing error of the gear mechanism (the forward-speed/reverse-speed changeover mechanism) connected to the rotating shaft. It is to be noted that, preferably, for example, a socket/spigot joint or knock-pin can be used as the fixing element.